* It is highly recommended to review the [http://wiki.archlinux.org/index.php/SSD#Tips_for_Minimizing_SSD_Read.2FWrites Tips for Minimizing SSD Read/Writes] on the [[SSD]] wiki article prior to selecting a filesystem. To sum up, ext4 with a journal should be fine. Recognize that flash has a limited number of writes, and a journaling file system will take some of these as the journal is updated. For this same reason, it is best to forgo a swap partition. Note that this does not affect installing onto a USB hard drive.

Configuration

Make sure that /etc/fstab includes the correct partition information for /, and for any other partitions on the USB key. Keep in mind the setup of the target machine when putting in the device names, as they may be different from the machine you are using for the installation. Example: if the installation machine has one hard drive, your USB key will likely be sdb. The target machine, however, may have no hard drives, in which case your USB key will likely be sda.

menu.lst, the Grub configuration file, should be edited to (loosely) match the following, replacing sda1 with the partition of the key on the target machine (note that, as grub is installed on the USB key, the key will always be hd0,0).

Regenerate the initrd image, kernel26.img. Edit /etc/mkinitcpio.conf, changing the hooks to include (at a minimum): "base udev ide usb filesystems" (Note: if using the 7.2 CD, and installing from the CD, you will have mkinitrd instead of mkinitcpio. During the configuration, you will be asked to edit mkinitrd.conf; simply change REMOVE_USB=1 to REMOVE_USB=0 and ignore the following command). Then rebuild the image by issuing:

Note: The kernel version (-k) must be the kernel version in the USB key, not the live cd's kernel version.

Tips

USB Support

Should you see that the /arch/setup correctly installed a system on to your USB drive but it stills failed to boot from it by complaining that it could not find the root file system even though it had been specified with UUIDs, then you are most likely missing support for USB. In this case, boot back into your Arch Setup CD/USB media and do the following:

chroot into the arch installation contained on the usb drive (don't forget the boot partition, if any)

Edit /etc/mkinitcpio.conf, and add "usb" to the "HOOKS=" line after udev:

HOOKS="base udev usb autodetect pata scsi sata filesystems"

Regenerate the initrd image by running:

# mkinitcpio -p kernel26

Using UUID

Instead of using literal partition names, you can also use the UUID of your partition. This way is much better and more manageable in a setup where the USB drive is meant to boot at multiple PC's than using the partition literal names (/dev/sdb1). Run:

# blkid

to find out which one points to the regular device node (ie, /dev/sdb1) that is your key.

Now you can place this device node (in the form UUID=7bf1d942-7b8c-4fb7-b55a-d3c40895906d) into /etc/fstab in place of the regular node (ie, /dev/sdb1). Edit also your kernel line in menu.lst, so it will contain something like:

And so forth, giving you the option to select a configuration for a wider variety of machines. However, changing the root= option in GRUB does not change /etc/fstab and you must do something (in our example using udev symlink), so the root partition will always be mounted correctly.

Run udevinfo -p /sys/block/sdx/ -a (where sdx is the device name of your usb key)

Make a new file: /etc/udev/udev.rules/10-my-usb-key.rules and insert: KERNEL=="sd**", SYSFS{product}=="DataTraveler 2.0", SYMLINK+="WHATEVERYOUWANTOTCALLIT%n" (KERNEL=="sd**" is because the kernel - 2.6.16 here - names all usb devices sd as it uses the scsi sub-system and you want to look at every sd device and apply the setting to every partition), with SYSFS{model}== being the unique identifier collected from udevinfo.

Run /etc/start-udev uevents and make sure the symlinks appears in /dev.